Projector utilizing compressed white signal

Abstract

In a projector having liquid crystal panels as light modulators, the liquid crystal panels are independently used for white-light modulation and colored-light modulation, respectively, so that high luminance and high resolution are compatibly attained. The projector has a liquid crystal panel which is driven by color signals, and which subjects light to colored-light modulation, and another liquid crystal panel which is driven by a luminance signal wherein a portion lower than a predetermined level is compressed by a compressing circuit, and which subjects light to white-light modulation. Modulated light outputted from the two liquid crystal panels are synthesized with each other in a polarized beam splitter, and the image of the synthesized light is formed on a screen by a lens. It is preferable that the color signal and the white signal which will be inputted to the liquid crystal panels are obtained from a composite video signal of the NTSC system.

What is claimed is: 
     
       1. A projector in which light modulation is conducted by liquid crystal panels in accordance with a video signal, comprising: a first signal circuit for obtaining a color signal from the video signal;   colored-light modulation means for conducting colored-light modulation according to the color signal, thereby obtaining colored light;   a second signal circuit for obtaining a white signal which indicates a white gradation, from the video signal;   a third signal circuit for compressing a portion of the white signal equal to or lower than a first level, thereby obtaining a compressed white signal;   white-light modulation means for conducting white-light modulation according to the compressed white signal, thereby obtaining white light; and   synthesizing means for synthesizing the colored light and the white light with each other.   
     
     
       2. A projector according to claim 1, wherein said first signal circuit includes color signal acquisition means for acquiring compressed color signals r, g, and b as said color signal, said compressed color signals being obtained by compressing portions of three primary color signals R, G, and B which have undergone gamma inverse correction, the portions being higher than a vicinity of a second level.   
     
     
       3. A projector according to claim 2, wherein said first level is different from said second level.   
     
     
       4. A projector according to claim 1, wherein a band of said color signal is narrower than a band of said compressed white signal.   
     
     
       5. A projector according to claim 2, wherein bands of said compressed color signals are narrower than a band of said compressed white signal.   
     
     
       6. A projector according to claim 1, wherein said first signal circuit includes means for adding color difference signals which have undergone gamma correction to a luminance signal which has undergone gamma correction, and means for obtaining said color signal by conducting gamma inverse correction on the added signals.   
     
     
       7. A projector according to claim 1, wherein said second signal circuit includes means for synthesizing color signals which have undergone gamma correction, thereby obtaining said white signal.   
     
     
       8. A projector according to claim 1, wherein said second signal circuit includes means for generating said white signal from an achromatic signal corresponding to a minimum value of three primary color signals R', G', and B' which have undergone gamma correction.   
     
     
       9. A projector according to claim 1, wherein said second signal circuit includes means for adding an achromatic signal to a luminance signal, the achromatic signal corresponding to a minimum value of color difference signals which have undergone gamma correction, and for producing said white signal from the added signal.   
     
     
       10. A projector according to claim 1, wherein said colored-light modulation means comprises a single liquid crystal panel consisting of three-primary color pixels.   
     
     
       11. A projector according to claim 1, wherein said colored-light modulation means comprises three liquid crystal panels for red, green and blue.   
     
     
       12. A projector according to claim 1, wherein said first signal circuit includes means for obtaining said color signal which has undergone gamma inverse correction, from a composite video signal, and said second signal circuit includes means for obtaining said white signal which has undergone gamma correction, from the composite video signal.   
     
     
       13. A projector according to claim 1, wherein said third signal circuit includes first signal processing means for compressing a signal at a level in the vicinity of said first level, said first signal processing means having a non-linear input/output characteristic.   
     
     
       14. A projector according to claim 13, wherein said first signal processing means comprises a diode.   
     
     
       15. A projector according to claim 13, wherein said first signal processing means is cascaded to extending means for extending a luminance signal which has undergone gamma correction.   
     
     
       16. A projector according to claim 2, wherein said third signal circuit includes first signal processing means for compressing a signal at a level in the vicinity of said first level, said first signal processing means having a non-linear input/output characteristic, and said color signal acquisition means includes second signal processing means for compressing a signal at a level in the vicinity of said second level, said second signal processing means having a non-linear input/output characteristic.   
     
     
       17. A projector according to claim 16, wherein said first and second signal processing means comprise a diode.